This invention is a variation of and an improvement over prior known vector thrust ducted propeller tail assemblies in which pivotable surfaces of the ducted tail rearwardly of the shrouded propeller deflect the propeller slip stream exiting from the rear of the duct in establishing a directional thrust for controlling yaw and flight condition of a rotary wing aircraft. This concept is most useful when utilized in a compound rotary wing aircraft in which the rotor is unloaded at a high speed cruising condition in which the fixed wing of the aircraft provides lift and the shrouded propeller provides forward thrust to the aircraft.
A number of patents have been issued directed to varying configurations of propeller slip stream deflecting surfaces that establish a rotor torque counterbalancing moment of the necessary magnitude required for yaw control and maintain the desired aircraft heading, U.S. Pat. Nos. 4,905,932; 3,260,482; 3,241,791 and 3,222,012 being typical. Although the ducted propeller ring tail configurations of these patents are suitable to establish a sufficiently high rate of turn of the aircraft both to the right and to the left in most situations, as explained in more detail in the Meyer U.S. Pat. No. 5,131,603 assigned to the assignee of this application, under low rotor shaft torque conditions rotor torque can be insufficient to establish a sufficiently high aircraft turning rate in the direction of rotor rotation for the aircraft to fulfill its mission. The invention of this application is directed to solving the same problems and improving the maneuverability of shrouded propeller ring tail aircraft as in U.S. Pat. No. 5,131,603 in which the combination of a shrouded propeller and duct deflecting surfaces creates a thrust force that can be exerted through a rearwardly extending arc of 180.degree.. In the invention of this application, a configuration of the pivotable duct deflecting surfaces captures the entire propeller slip stream and directs the exit flow in a manner as creates a smoother flow pattern with lesser turbulence and greater aerodynamic efficiency than the configuration of U.S. Pat. No. 5,131,683.